Can fog firefighting systems beat sprinklers?
It seems that fog fire fighting systems have a way to go to catch up with sprinklers as far as popularity is concerned, but there’s good reason to consider them.
As Andrea Davanzo of Sweden’s Ultrafog AB explained, the ultrafine mist produced by the stainless steel head cools the space, mitigates against radiant heat and suppresses the oxygen available for the flames. More, it does all this only using 10% of the volume of water of a sprinkler system: the surface area provided by millions of very high-density water droplets is much greater than that presented by larger splashes.
The fact that it doesn’t drench the area “means you are more quickly able to return to duty – and there’s less repair work”. In fact Mr Davanzo added that the suspended water droplets display a tendency to “surge” around the flames, drawn in by the hot air flow, “which means that the fog tends to stay localised”.
The high pressure fog also wins when it comes to installation: as one nozzle can protect an area up to 48m2, there are fewer to be installed and the narrow gauge pipe results in a low total weight.
While these systems are obviously of practical use throughout accommodation and galley areas onboard personnel carriers such as the larger CTVs as well as in vessels such as SOVs and other floatels, more novel is the fire-fighting fog’s ability to protect structurally vulnerable areas with its cooling properties.
For example, one installation focused on the underwater viewing area of a sightseeing boat: While strong enough in normal conditions “the glass stood the chance of breaking if exposed to intense heat” Mr Davanzo explained, compromising the integrity of the whole vessel.
The answer was to use fog to keep the temperature down, making it safe even in case of fire.
Finally, these fog units are also effective enough to be Lloyd’s Register certified for use against fires in Category A machinery spaces, i.e. engine rooms. While they take a little longer that gas to completely extinguish the fire – minutes rather than seconds – once it’s out, it’s out, explained Mr Davanzo’s colleague, Przemyslaw Zalucki, unlike gas which just blocks oxygen, and so demands maintained concentration or risks the fire reigniting.
Further, Mr Zalucki added: “The big advantage of water mist over CO2 is that someone who stays in the engine room, dies.” So, while there are other, expensive alternatives to CO2, mist remains the less toxic, cheaper solution.
By Stevie Knight
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